Connexion throws error: AttributeError: module 'typing' has no attribute 'GenericMeta' while using python 3.7.0

[tniharika]

Description

While using python 3.7.0 with Swagger 2.0 server side python-flask code, we are getting the error "AttributeError: module 'typing' has no attribute 'GenericMeta'"
See line number 12

---Code---
1 def add_procedure(ProcedureItem=None): # noqa: E501
2 """adds an Procedure item
3
4 Adds an item to the system # noqa: E501
5
6 :param ProcedureItem: Procedure item to add
7 :type ProcedureItem: dict | bytes
8
9 :rtype: None
10 """
11 if connexion.request.is_json:
12 ProcedureItem = proc_item.from_dict(connexion.request.get_json()) # noqa: E501 -> Error here
13 return 'do some magic!'

Expected behaviour

Has to process the request and return " do some magic!"

Actual behaviour

throwing error at line 12
"AttributeError: module 'typing' has no attribute 'GenericMeta'"

Steps to reproduce

Download swagger python flask server side code and run with python 3.7

Additional info:

We ran the same file with python 3.6.7 and it worked as expected and returned, "do some magic!"

Output of the commands:
Just read the README document while downloading from swagger

[jmcs]

Can you post the entire exception?

[cassinaooo]

Hi @jmcs , here's a complete Trace:

Looks somewhat related to sphinx-doc/sphinx#4490

I think I can get away with editing util.py by myself, will try and post the results.

I also think it is a swagger-code-gen issue, if it is a connexion issue, I could try a PR if you guide me through it.

-------------------- >> begin captured logging << --------------------
flask.app: ERROR: Exception on /v1/orders/1000/invoices [PUT]
Traceback (most recent call last):
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/connexion/decorators/decorator.py", line 66, in wrapper
    response = function(request)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/connexion/decorators/validation.py", line 122, in wrapper
    response = function(request)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/connexion/decorators/validation.py", line 293, in wrapper
    return function(request)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/connexion/decorators/decorator.py", line 42, in wrapper
    response = function(request)
  File "/home/lightbringer/scudra/scudra-backend-api/.tox/py37/lib/python3.7/site-packages/connexion/decorators/parameter.py", line 218, in wrapper
    return function(**kwargs)
  File "/home/lightbringer/scudra/scudra-backend-api/api/controllers/orders_controller.py", line 64, in orders_order_id_invoices_put
    api_invoice = Invoice.from_dict(connexion.request.get_json())  # noqa: E501
  File "/home/lightbringer/scudra/scudra-backend-api/api/models/invoice.py", line 69, in from_dict
    return util.deserialize_model(dikt, cls)
  File "/home/lightbringer/scudra/scudra-backend-api/api/util.py", line 110, in deserialize_model
    setattr(instance, attr, _deserialize(value, attr_type))
  File "/home/lightbringer/scudra/scudra-backend-api/api/util.py", line 25, in _deserialize
    elif type(klass) == typing.GenericMeta:
AttributeError: module 'typing' has no attribute 'GenericMeta'
--------------------- >> end captured logging << ---------------------

Thanks a lot for the the lib. :)

[cassinaooo]

Ok, if anyone have the same problem, you can edit util.py in the following way:

Change

elif type(klass) == typing.GenericMeta:
    if klass.__extra__ == list:
        return _deserialize_list(data, klass.__args__[0])
    if klass.__extra__ == dict:
        return _deserialize_dict(data, klass.__args__[1])

In util.py , to

elif hasattr(klass, '__origin__'):
    if klass.__origin__ == list:
        return _deserialize_list(data, klass.__args__[0])
    if klass.__origin__ == dict:
        return _deserialize_dict(data, klass.__args__[1])

I used some google-fu and found this answer in stack overflow

[dtkav]

@willianscfa Is that change backward compatible with python 2.7 / 3.5 / 3.6?

[cassinaooo]

Unfortunately not @dtka. In python < 3.7 it worked just fine using __extra__. This error appeared for me after I had to upgrade to python 3.7 while maintaining code generated using swagger-code-gen because of a generic type serialization issue. See python/typing#511.

This is a breaking change within the typing module itself. However, the commit associated with the sphinx issue linked above uses a backward compatible solution. They specifically check for the python version before accessing some properties. See tk0miya/sphinx@e2389b4.

Anyway, util.py is a file generated by swagger-code-gen, and any solution (backwards compatible or not), should be implemented by them. See an example: https://github.com/swagger-api/swagger-codegen/blob/master/samples/server/petstore/flaskConnexion/swagger_server/util.py. In any case I think I will problably open an issue there and see if someone could guide me through a first PR. =)

[dtkav]

ok awesome. I'll close the issue against connexion for now then.
Thanks for the detailed explanation!

[GioPat]

Ok, if anyone have the same problem, you can edit util.py in the following way:

Change

elif type(klass) == typing.GenericMeta:
    if klass.__extra__ == list:
        return _deserialize_list(data, klass.__args__[0])
    if klass.__extra__ == dict:
        return _deserialize_dict(data, klass.__args__[1])

In util.py , to

elif hasattr(klass, '__origin__'):
    if klass.__origin__ == list:
        return _deserialize_list(data, klass.__args__[0])
    if klass.__origin__ == dict:
        return _deserialize_dict(data, klass.__args__[1])

I used some google-fu and found this answer in stack overflow

By using this modification I have problem with python 3.6.5 in deserializing subobjects.
I am trying to find another solution!
Solved with

 elif hasattr(klass, '__origin__'):
     if klass.__origin__ == list or klass.__origin__ == typing.List:
         return _deserialize_list(data, klass.__args__[0])
     if klass.__origin__ == dict:
         return _deserialize_dict(data, klass.__args__[1])